Furnace structure



Aug. 2s, 1922 1,682,328

. R. A.I FORESMAN l Funmca sTRucTunE Filed April 12,V 1925` mvENToRATTORNEY CAD Patented Aug. 28, 1928.

UNITED STATES PATENT OFFICE.'

ROBERT A. FORESMAN, OF MOORE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA,

EURNACE STRUCTURE.

Application filed April 12,

This invention relates to underfeed stoker furnaces and has for itsobject to provide a furnace of the character designated which shalleconomically burn low grade fuels such as lignite and coke braize. Ithas for a further object the ready ignition of t-he green entering fueland the maintenance of uniform combustion conditions throughout the fuelbed by the employment of a refractory arch overlying the fuel bed forthe purpose of radiating heat to and causing a portion of the heatedgases from the high temperature sections of the fuel bed to pass overthe green fuel, and at the same time permitting a major portion of thefurnace gases to pass directly to the heat absorbing s urfaces of theboiler or other units utilizing the heat of the furnace.

These and other objects of my invention which are made more manifest inthe further description thereof, may be attained by the employment ofthe apparatus illustrated in the accompanying drawing in which Iilig. lis a diagrammatic sectional representation of an underfeed furnaceequipped with a refractory arch in accordance with the presentinvention; and F ig. 2 is a view in section on line IIII of Fig. 1.

It has heretofore been considered impracticable. to burn lignites orcoke braizes successfully on an underfeed stoker, for the reason thatthese fuels ignite with difficulty and tend to drift toward the rear ofthe fire boX, resulting in a failure to maintain a sufficiently uniformcombustion condition throughout the entire fuel bed for the economicalcombustion of these fuels. I have found that in practice these lowgrade, drifting fuels can be burned satisfactorily by disposing an archabove the fuel bedand spaced from the front wall and the bridge wall,the resulting passages being so proportioned that a sufficient quantityof the heated furnace gases sweeps forwardly over the entering fuel toassist in the maintef nance of active combustion on forward portions ofthe stoker grate. I have also found it to be desirable when burningthese low grade fuels to admit air or steam, or both.v in regulatablequantities over the fuel bed at the bridge wall of the furnace. This1923. Serial No. 631,665.

serves to retard the rearward drifting of the fuel to mixthe gases andsecure a more complete combustion of their combustible constituents. Insome installations, it niav be desirable also to adiiiit air at thefront walls of the furnace.

Referring to the drawing I show a furnace 10 housing an underfeed stoker11 and a boiler 12 of the Stirling type. The furnace comprises a frontwall 14, a bridge wall 15, and side walls 16 of usual construction. Theunderfeed Stoker is of the well known multiple retort type and comprisesa hopper 20, retorts 21, twyer banks 22, and dump grates 23. The normalcontour of the fuel bed is designated by the line 25.

The baffle member or refractory arch extends the full width of thefurnace, and is spaced from the front wall 14 and the fuel bed 25 asufficient distance to permit a portion of the heated furnace gases fromzones of most active combustion'to pass forwardly under the arch andover the incoming fuel and then upwardly between the front wall of thefurnace and the arch.

.As illustrated, the arch is of a hollow, air-cooled construction, builtin the following manner: Two pairs of channel beanis 31 are supported inthe side walls of the furnace, each pair having the flanges of the beamsinwardly directed to provide a slot 3Q in which T-hangers 33 aresuspended. The base of the arch is formed of a plurality of rows ofrefractory tile 35 supported by T-beams 36 which lock into an undercutgroove 37 in the upper portion of eacli tile. The several rows of tilesare assenibled transversely to the channel beams 31 and are suspendedtherefrom by a detachable connection 38, which secures the T- beams 36to the lower ends of the hangers 33. Side walls 10 of the` arch arecarried by the end tiles 35 and are preferably of refractory brickcobbled inwardly toward the top of therv arch. The top wall of the archis supported upon lintelsl lwhich rest on the beams 31, a fire brick 43being interposed to cut down the heat transfer between the beamsv 31 andthe lintels.

Tiles 45 are carried by the lintels 42 and one or more layers of firebrick are laid upon the tiles 45. Openings 46 in the side walls 16 leadinto the interior of the baffle and permit the circulation of airtherethrough for cooling the arch structure. The 'air thus heated mayadvantageously feed to the furnace grate. l

It is to be understood, however, that the above described arch structureis merely illustrative of one form of baffle member adapted for carryingout my invention, and that my invention is not limited to the specilicarch structure employed.

Twyers are provided in the front wall of the furnace and twyers 51 inthe bridge wall, through which twyers, air or steam under pressure maybe directed above the fuel bed to assist in the combustion of thefurnace gases. lThe air or steam is supplied to the tuyere 50 by meansof a conduit 52 formed in the front wall lll, and is supplied to thetuyres 5l by a conduit 53 formed in the bridge wall l5.

From the foregoing description the 1nanner in which my invention ispracticed is apparent. In brief, assuming that the furnace is inoperation and that coke braize, or other low grade fuel, is being fedinto the retorts 21 from the hopper 20, the entering green fuel, whichnormally would travel a considerable distance toward the rear of thefurnace, due to the drifting character of these fuels, before beingfully ignited,`s subjected to the heat of a continuous stream of heatedgases from the zones of active combustion. These highly heated gases,together with'radiated heat from the arch, quickly ignite the incomingfuel, and as a result a more nearly uniform combustion conditionprevails throughout the fuel bed than has been possible to attainheretofore. The air or steam flowing through the tuyres 5l will forcethe lighter particles of fuel towards the front of the fuel bed and willthus overcome the tendency of this fuel to drift towards the rear of thefurnace. It is to be noted that in some instances the coke braise orother low-grade fuel is mixed with a bituminous coal. In such a case myimproved construction has an additional advantage in that the colring ofthe fuel will commence at a point closer to the front wall of thefurnace and will thus aid in retarding the objectionable shifting of thefuel tewards the rear, before it is in condition to be ignited.

A circulation of air through the arch 30 can be maintained by induced orby force draft mechanism. Thus, the air for combustion may be drawnthrough the arch to the air blower which supplies air to the furnacegrate, or the air from the blower may be passed in whole or in partthrough the arch prior to delivery to the furnace grate.

While it is not essential to good operation in the furnace abovedescribed, jets of modifications, without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are specificallyset forth in the appended claims.

What I claim is:

1. In a furnace having the usual front, side and bridge walls, thecombination with an underfeed Stoker of the multiple retort type havinga generally inclined fuel bed from the front wall to the bridge wall, ofa refractory baille spaced from the fuel bed, the front wall and thebridge wall in such manner that the furnace gases are directed from thefuel bed in two distinct paths of travel, one path extending forwardlyand upwardly between the frontwall and the baille, and the other pathextending upwardly between the bridge wall and the baffle and means forinjecting ets of oxygenbeaing fluid into the gases in the said other pat2. In a furnace having the usual front, side and bridge walls, thecombination with an underfeed Stoker of the multiple retort type havinga generally inclined fuel bed from the front wall to the bridge wall, ofa refractory baffle spaced from the fuel bed, the front wall and thebridge wall in such manner that the furnace gases are directed from thefuel bed in two distinct paths of travel, one path extending forwardlyand upwardly between the front wall and the baffle, and the other pathextending upwardly between the bridge wall and the baille, means forinjecting jets of oxygenbearing fluid into the gases in the said onepath, and means for injecting jets of oxygen-bearing fluid into thegases in the said other path.

3. In a furnace having the usual front, side and bridge walls, thecombination with an underfced stolrer of the multiple retort type havinga generally inclined fuel bed from the front wall to the bridge wall, ofa refractory baffle spaced from the fuel bed, the front wall and thebridge wall in such manner that the furnace gases are directed from thefuel bed in two distinct paths of travel, one path extending forwardlyand upwardly between the front wall and the baille, and the' other pathextending upwardly between the bridge wall and the4 baflle and meansassociated with the bridge wall for injecting jets of oxygen-bearing uidinto the gases immediately over the fuel bed in a direction counter tothe travel of the fuel through the furnace.

4. In a furnace, the combination with a progressive feed grate on Whichfuel is fed at the front of the furnace and then rear- Wardly anddownwardly to discharge, of a refractory baille arranged directly aboveand adjacent to the fuel bed, and means associated With the furnace forinjecting oxygen- 10 In testimony whereof, I have hereunto 15 subscribedmy name this 9th day of April, 1928.

ROBERT A. FORESMAN.

